Alphasense Application Note AAN 009 AAN009 HOW OXYGEN SENSORS WORK Galvanic oxygen sensors are the most popular technology for measuring oxygen concentration in air. These oxygen sensors can be divided into two types: • • Mass flow control using capillary Partial pressure control using solid polymer membrane Oxygen Sensor Chemistry Alphasense oxygen sensors operate like a metal/air battery. Since oxygen is reduced at the cathode, the partial pressure on the cathodic side of the membrane is virtually zero, giving a driving force which is linearly dependent on oxygen partial pressure, so the rate of gas diffusion (and hence sensor output) is linearly dependent on the oxygen partial pressure.